C#•3mo ago

WPF Treeview HierarchicalDataTemplate on Type with sub-collection

Hi Folks. I have the following two models (abridged for brevity) and mainViewModel:

internal class Gist
{
    public ObservableCollection<GistFile> GistFiles { get; set; } = new();

    public override string ToString()
    {
        return GistFiles.OrderBy(gf => gf.Filename).First().Filename;
    }
}

internal class GistFile
{
    public string Filename {  get; set; }

    public override string ToString()
    {
        return Filename;
    }
}

internal class MainWindowViewModel : ViewModelBase
{
    private ObservableCollection<Models.Gist> gists = new ObservableCollection<Models.Gist>();
    public ObservableCollection<Models.Gist> Gists { get => gists; set => SetProperty(ref gists, value); }    
}

internal class Gist
{
    public ObservableCollection<GistFile> GistFiles { get; set; } = new();

    public override string ToString()
    {
        return GistFiles.OrderBy(gf => gf.Filename).First().Filename;
    }
}

internal class GistFile
{
    public string Filename {  get; set; }

    public override string ToString()
    {
        return Filename;
    }
}

internal class MainWindowViewModel : ViewModelBase
{
    private ObservableCollection<Models.Gist> gists = new ObservableCollection<Models.Gist>();
    public ObservableCollection<Models.Gist> Gists { get => gists; set => SetProperty(ref gists, value); }    
}

and my xaml:

<TreeView x:Name="GistsTV"  ItemsSource="{Binding Gists}" Width="200">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Gists.Files}">
            <TextBlock Text="{Binding}"></TextBlock>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

<TreeView x:Name="GistsTV"  ItemsSource="{Binding Gists}" Width="200">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Gists.Files}">
            <TextBlock Text="{Binding}"></TextBlock>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

I'm only getting the Gist displayed and not the GistFiles on a sub-level. I know I'm getting this wrapped around my head conceptually - what am I doing wrong?

1 Reply

stigzler•3mo ago

For clarity - I'm wanting Gists to display at the root level and them GistFiles to display at the child level Bingo:

<DockPanel>
    <DockPanel.Resources>
        <HierarchicalDataTemplate DataType="{x:Type models:Gist}" ItemsSource="{Binding Path=GistFiles}">
            <TextBlock Text="{Binding Id}"></TextBlock>
        </HierarchicalDataTemplate>
        <DataTemplate DataType="{x:Type models:GistFile}">
            <TextBlock Text="{Binding Filename}"></TextBlock>
        </DataTemplate>
    </DockPanel.Resources>
    <TreeView x:Name="GistsTV"  ItemsSource="{Binding Gists}" Width="200">
    </TreeView>
</DockPanel>

<DockPanel>
    <DockPanel.Resources>
        <HierarchicalDataTemplate DataType="{x:Type models:Gist}" ItemsSource="{Binding Path=GistFiles}">
            <TextBlock Text="{Binding Id}"></TextBlock>
        </HierarchicalDataTemplate>
        <DataTemplate DataType="{x:Type models:GistFile}">
            <TextBlock Text="{Binding Filename}"></TextBlock>
        </DataTemplate>
    </DockPanel.Resources>
    <TreeView x:Name="GistsTV"  ItemsSource="{Binding Gists}" Width="200">
    </TreeView>
</DockPanel>

I guess WPF hooks hem all up in the background For completness:

internal class GistFilesToFirstFilenameConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {

        ObservableCollection<Models.GistFile> gistFiles = (ObservableCollection<Models.GistFile>) value;
        if (gistFiles.Count > 0)
        {
            return gistFiles.First().Filename;
        }

        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

internal class GistFilesToFirstFilenameConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {

        ObservableCollection<Models.GistFile> gistFiles = (ObservableCollection<Models.GistFile>) value;
        if (gistFiles.Count > 0)
        {
            return gistFiles.First().Filename;
        }

        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

<converters:GistFilesToFirstFilenameConverter x:Key="GistFilesToFirstFilenameConverter"/>

<DockPanel Width="Auto">
    <DockPanel.Resources>
        <HierarchicalDataTemplate DataType="{x:Type models:Gist}" ItemsSource="{Binding Path=GistFiles}">
            <TextBlock Text="{Binding GistFiles, Converter={StaticResource GistFilesToFirstFilenameConverter}}"></TextBlock>
        </HierarchicalDataTemplate>
        <DataTemplate DataType="{x:Type models:GistFile}">
            <TextBlock Text="{Binding Filename}"></TextBlock>
        </DataTemplate>
    </DockPanel.Resources>
    
    <TreeView x:Name="GistsTV"  ItemsSource="{Binding Gists}">
    </TreeView>
    
</DockPanel>

<converters:GistFilesToFirstFilenameConverter x:Key="GistFilesToFirstFilenameConverter"/>

<DockPanel Width="Auto">
    <DockPanel.Resources>
        <HierarchicalDataTemplate DataType="{x:Type models:Gist}" ItemsSource="{Binding Path=GistFiles}">
            <TextBlock Text="{Binding GistFiles, Converter={StaticResource GistFilesToFirstFilenameConverter}}"></TextBlock>
        </HierarchicalDataTemplate>
        <DataTemplate DataType="{x:Type models:GistFile}">
            <TextBlock Text="{Binding Filename}"></TextBlock>
        </DataTemplate>
    </DockPanel.Resources>
    
    <TreeView x:Name="GistsTV"  ItemsSource="{Binding Gists}">
    </TreeView>
    
</DockPanel>

Gaming

Programming

WPF Treeview HierarchicalDataTemplate on Type with sub-collection